The effects of captivity on the morphology of captive, domesticated and feral mammals

1 The effects of captivity on the behaviour of wild and domestic animals have been relatively well studied, but little has been published on morphological changes in wild animals in captivity. We review the evidence for changes in a wide variety of mammalian taxa, with non-mammalian examples where relevant. 2 We consider the morphological effects of the process of domestication, and compare changes in both hard and soft tissues in captive and domestic animals with those in their wild counterparts. These include skull shape differences, brain size reduction, postcranial adaptations and digestive tract changes. 3 We also summarize studies that have looked at morphological change in feral animals in comparison with their wild and domestic ancestors, and consider their use as an analogue for morphological change in captive-bred animals that have been released into the wild. 4 We then discuss the importance of this work for the wider aims of conservation of endangered species and captive breeding over many generations, and emphasize the importance of studying these changes now, while for many species, the process is just beginning rather than many generations down the line, or immediately prior to release, where survival of captive-bred animals may be severely compromised.